cms physics beyond ls1chlebana/cms/hcalupgrade/... · i’ll use two meanings of the word physics...

CMS Physics Beyond LS1

Christopher S. Hill (OSU)CMS Workshop on High Luminosity LHCAlushta, UkraineMay 28th 2012

1Monday, May 28, 12

I’ll use two meanings of the word physics in this talk

• Part 1 - Physics (with capital “P”) beyond LS1• Measurements/searches that we must perform at 14 TeV w. 300 fb-1, 3000 fb-1

• Difficult because necessarily speculative - we do not yet know what will be the burning physics questions (though we have some hints and general ideas)

• Even these have not been studied very much (yet)• Part 2 - physics (with a lower case “p”) beyond LS1, i.e. CMS physics

organization (PAGs, POGs, etc) for the future• Perhaps less interesting, but it is important to discuss how to get prepared/

organized to perform needed physics studies to inform physics program (and related upgrades) post LS1

• This process has started, and I will give an overview of the status and future plans of this activity

• Potentially recruit new CMS collaborators to participate

2Monday, May 28, 12

Part 1: Physics

3Monday, May 28, 12

What physics do we need to be ready to do with CMS post LS1?

• We should target the important physics questions that we will face in the next decade or so

• While I don’t have a crystal ball, 2011 data from the LHC has already given hints about where the physics that we should target may/may not be

• We can speculate based on this but i think it is important to note that for the first time in a long time in HEP collider physics,

• We will know a great deal more about which direction to go very soon

• Possibly in as little as few months, but almost certainly by the time all the 2012 data are analyzed

• However, given this caveat, I will tell you my thoughts

4Monday, May 28, 12

• What is the nature of electroweak symmetry breaking? Is this related to the origin of mass of the fundamental particles in the SM?

• Long favored answer is Higgs mechanism, but then we must find a SM higgs boson

• As I am sure you are aware, we have seen some hints and soon we will have the (beginning of) the experimental answer to this question

• Is there a natural solution to the hierarchy problem? Or not?

• Those are the big two for which LHC was built, (there are others below that we could get lucky and address, but they do not drive the LHC program (nor our upgrades, unless we see a signal …)

• Are the particles of the SM fundamental?• Only 4 forces? Can they be unified?• What about gravity?• What is dark matter? e.g. SUSY LSP?

Recall the main questions in physics we hope to address with CMS data

SM is a correct but incomplete description of Nature

5Monday, May 28, 12

Higgs boson mass (GeV)110 115 120 125 130 135 140 145

SMσ/

σ95

% C

L lim

it on

-110

1

10 ObservedExpected (68%)Expected (95%)

ObservedExpected (68%)Expected (95%)

-1L = 4.6-4.8 fb = 7 TeVsCMS Preliminary,

What we will know as we head into LS1

• We will know a lot about the first big question (EWSB):

• We will have either discovered a particle that is a candidate Higgs boson

• We will have measured its mass, perhaps ~125 GeV

• In which case we will have made preliminary measurements of sigma x BRs

• But,these will not be precise enough to conclusively demonstrate it is a SM Higgs

• OR we will have ruled out a SM Higgs boson over the entire plausible mass range

G. Tonelli, CERN/INFN/UNIPI HIGGS_CERN_SEMINAR December 13 2011 38

Freshly squeezed EWK plots

6Monday, May 28, 12


SM Higgs production at LHC

Gluon fusion (gg H) is the dominant production mechanism at LHC.

Irreducible backgrounds in H WW, ZZ, γγ are from qq annihilation. Signal to Noise

better than at Tevatron except in VH. VBF and VH also very useful at LHC

How long will it take to confirm the properties of SM higgs?

• We should be able to measure sigma x BR ~20% in the γγ mode during 2015-2017 run

• Other modes will take longer, post LS2

• Should also be able to measure the spin

• H to ZZ to leptons

10.3. Discovery reach 325

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Figure 10.35: Left: Precision on the measurement of the product of cross-section and branch-ing ratio as a function of the integrated luminosity with LHC running at high luminosityfor a 120 GeV/c2 Higgs boson. Right: Statistical significance for different Higgs boson masshypotheses as a function of the integrated luminosity with LHC running at high luminosity.The 1� systematic uncertainty is represented by the grey band.

)2 (GeV/cHm90 100 110 120 130 140 150

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Figure 10.36: Statistical significance (left) and luminosity needed for a 5� or 3� observation(right) as a function of mH. The 1� systematic uncertainty is represented by the grey band.

10.3.2 Discovery reach for the Standard Model Higgs boson

This section summarises the discovery reach for the Standard Model Higgs boson. The NLOcross sections and branching ratios for the Higgs boson calculated with the programs HDE-CAY [41], HIGLU [40], VV2H, V2HV and HQQ [20] are used, as well as the NLO cross sectionsfor the background processes, when available.

Figure 10.38 shows the integrated luminosity needed for the 5� discovery of the inclusiveHiggs boson production pp ! H + X with the Higgs boson decay modes H ! ��, H !ZZ! 4`, and H!WW! 2`2⌫.

Figure 10.39 shows the signal significance as a function of the Higgs boson mass for 30 fb�1

of the integrated luminosity for the different Higgs boson production and decay channels.

From CMS PTDR


SM Higgs Decay Modes Vs Mass

Mode Mass Range Data Used (fb-1) CMS Document

H γγ 110-150 4.7 HIG-11-030

H bb 110-135 4.7 HIG-11-031

H ττ 110-145 4.6 HIG-11-029

H WW 2l 2ν 110-600 4.6 HIG-11-024

H ZZ 4l 110-600 4.7 HIG-11-025

H ZZ 2l2τ 190-600 4.7 HIG-11-028

H ZZ 2l2j 130-165/200-600 4.6 HIG-11-027

H ZZ 2l2ν 250-600 4.6 HIG-11-026

328 Chapter 10. Standard Model Higgs Bosons

ZZ

e

e!

+µ+

µ!

!1

! 221

"

#

Figure 10.40: Definitions of the angles in the �! ZZ! e+e�µ+µ� process.

rest frame, between momentum of negatively charged lepton and the direction of motion ofZ boson in the Higgs boson rest frame (Figure 10.40).

The analysis was performed for scalar, pseudoscalar and CP-violating Higgs boson states,the latter for tan ⇠=±0.1, ±0.4, ±1 and ±4.

A detailed description of the analysis can be found in [515].

10.3.3.1 Generation and event selections

The production and decay of the scalar, pseudoscalar and CP-violating Higgs boson stateswere generated using PYTHIA [69] for three masses of the Higgs boson, M� = 200, 300 and400 GeV/c2. Backgrounds and event selections are the same as in the analysis of the StandardModel Higgs boson H ! ZZ ! e+e�µ+µ� described in Section 10.2.1. The reconstructedangular distributions after all selections for the signal with mass M�=300 GeV/c2 for variousvalues of the parameter ⇠, and for the background are shown in Figure 10.41 at 60 fb�1. TheStandard-Model signal cross-section and branching ratio were used for the signal normali-sation in Figure 10.41.

!0 0.5 1 1.5 2 2.5 3

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Figure 10.41: The '-distributions (left) and the ✓-distributions (right) for various values of theparameter ⇠ after final selections at 60 fb�1. Empty histograms - the signal for M�=300 GeV/c2

and ⇠=0 (scalar), ⇠ = �⇡/4, ⇠ = +⇡/4 and |⇠| = ⇡/2 (pseudoscalar). The filled histogram -the ZZ background. The Standard-Model signal cross-section and branching ratio were usedfor the signal normalisation.

7Monday, May 28, 12

To get to ~10% precision need HL-LHC

• Model independent measurements through ratios of rates for two different final states• Higgs cross-section, total width and luminosity cancel• Can get to ~10% precision in most measurements with HL-LHC

17

H→γγ/H→ZZ

H→WW/H→ZZ

ttH→γγ/ttH→bb

qqH→WW/ttH→ττ

WH→WWW/H→WWWH→γγ/H→γγ

H γγ

HW+

W-W

γγ+

f

(a)

(a) Indirect. Extracts HWW from H→γγ:

No estimate of precision for direct H→WW/H→ZZ

(b) Need to reassess tt+H→bb

(b) (c)

(c) Assumed to be TH-systematics limited (in particular, no improvement at SLHC). Review systTH, also in view of forthcoming LHC data

From the 2002 SLHC study (Gianotti, Mangano, Virdee et al, EPJC, hep-ph/0204087)

mH=125 mH=125

hep-ph/02040878Monday, May 28, 12

Next big question is Naturalness

• If MH is ~125, this has implications for (natural) SUSY

• In (e.g MSSM), the lightest higgs can be 114-135, so 125 naively seems perfect

• However, in MSSM, higgs mass is

• Even at large tanβ, the correction term must be ~87 GeV

• Requires (comparatively modest) fine tuning

• Or non-miminal SUSY (e.g. NMSSM)

• (Or both)

1 Introduction

The ATLAS and CMS Collaborations have recently presented the first evidence for a Higgs boson

with a mass of ⇠ 126 GeV [1, 2]. The �� channel yields excesses at the 2–3 � level for ATLAS

and CMS, insu�cient for a clear discovery. Yet the concordance between the ATLAS and CMS

excesses increases the likelihood that this is indeed the Higgs boson, and motivates us to study

the implications for natural electroweak breaking in the context of weak-scale supersymmetry.

In the Minimal Supersymmetric Standard Model (MSSM) the lightest Higgs boson is lighter

than about 135 GeV, depending on top squark parameters (for a review with original references,

see [3]), and heavier than 114 GeV, the LEP bound on the Standard Model Higgs [4]. A Higgs

mass of 126 GeV naively seems perfect, lying midway between the experimental lower bound and

the theoretical upper limit. The key motivation for weak-scale supersymmetry is the naturalness

problem of the weak scale and therefore we take the degree of fine-tuning [5, 6, 7, 8, 9] as a

crucial tool in guiding us to the most likely implementation of a 126 GeV Higgs. In this regard

we find that increasing the Higgs mass from its present bound to 126 GeV has highly significant

consequences. In the limit of decoupling one Higgs doublet the light Higgs mass is given by

m2

h = M2

Z cos2 2� + �2t (1)

where �2t arises from loops of heavy top quarks and top squarks and tan � is the ratio of elec-

troweak vacuum expectation values. At large tan �, we require �t ⇡ 87 GeV which means that

a very substantial loop contribution, nearly as large as the tree-level mass, is required to raise

the Higgs mass to 126 GeV.

The Higgs mass calculated at two loops in the MSSM is shown in Figure 1 as a function of

the lightest top squark mass for two values of the top squark mixing parameter Xt. The red/blue

contours are computed using the Suspect [10] and FeynHiggs [11] packages, which have di↵ering

renormalization prescriptions and the spread between them, highlighted by the shading, may

be taken as a rough measure of the current uncertainty in the calculation. For a given Higgs

mass, such as 126 GeV, large top squark mixing leads to lower and more natural top squark

masses, although the mixing itself contributes to the fine-tuning, as we will discuss. In fact,

stop mixing is required to raise the Higgs mass to 126 GeV without multi-TeV stops. Even at

maximal mixing, we must havepmQ3mu3 & 700 GeV (which, for degenerate soft masses, results

in squark masses hundreds of GeV heavier than have been directly probed by existing LHC

searches [12, 13]) and, as we will discuss in the next section, this implies that fine-tuning of at

least 1% is required in the MSSM, even for the extreme case of an ultra-low messenger scale of

10 TeV. Hence we seek an alternative, more natural setting for a 126 GeV Higgs.

In the next-to-minimal model (NMSSM, for a review with references, see [14]) the supersym-

metric Higgs mass parameter µ is promoted to a gauge-singlet superfield, S, with a coupling to

1

Is SUSY Natural?

Natural Unnatural

m̃� v m̃� v

mh125 150 100

Natural Unnatural

We simply don’t know

125 is close to the Z mass… but not close

enough

L. Hall, SavasFest 2012

9Monday, May 28, 12

• Must continue the squark/gluino searches at least until we have reached the naturalness limit (~1.5 TeV)

• Targeted searches for 3rd generation squarks (stops & sbottoms) are needed/being performed

• Signatures are more difficult, especially single stop/sbottom

• Irreducible top backgrounds

• If fail to see light stops, essentially have to give up naturalness

• Of course if do observe light stops, requirements on upgraded detector to study them are “familiar” (from top physics)

Natural SUSY in 2012 and beyond LS1

SUSY status report, David Stuart (UCSB) ‏" 29!

Interpreting limits – and next steps

N. Arkani-Hamed, “Implications of LHC results for TeV-scale physics”

Must cover stealth SUSY, RPV scenarios too

t̃ ! b�̃1± ! b�̃1

0`⌫

10Monday, May 28, 12

Other “Natural” Solutions still possible• Another solution to the hierarchy problem is

extra spatial dimensions

• Remember the hierarchy problem is that if one computes the quadratic corrections to the higgs mass, cut off at a scale Λcutoff ~ MPl the fine tuning required to get an ~100 GeV Higgs is extreme

• This is because MPl is a big number

• Extra-dimensions (n of them, of radius R) simply make true n-dim MPl a smaller number

ADD scenario:

V (r) � m1m2

Mn+2Pl(4+n)

1rn+1

, (r ⇥ R)

V (r) � m1m2

Mn+2Pl(4+n)R

n

1r, (r ⇥ R)

M2Pl �Mn+2

Pl(4+n)Rnbig #

smaller # times factorFig. 18: Expected 5! discovery reach on the gravity scaleMD as a function of the number of extra-dimensions " in ATLAS inthe framework of ADD models, for 100 fb!1 (LHC) and 1000 fb!1 (SLHC).

4.7.2 Virtual graviton exchange in ADD modelsVirtual KK gravitons can also be exchanged between incoming and outgoing SM particles in high-energycollisions, thereby leading to modifications of the cross-section and angular distributions compared tothe SM expectations. Since graviton effects are enhanced at high energy, due to the large number ofaccessible Kaluza-Klein excitations, such manifestations of Extra-dimensions are expected at large in-variant mass and pT of the particles in the final state. Drell-Yan and two-photon production are amongthe most sensitive channels at high-energy colliders. Using these channels, it was found that the reachin the gravity scale MD for ! = 3 increases from !8 TeV (100 fb!1, standard LHC) to 11.7 TeV (3000fb!1, SLHC).

4.7.3 Resonance production in Randall-Sundrum modelsIn the Extra-dimension scenario proposed by Randall and Sundrum [38] the hierarchy between the Planckand the electroweak scales is generated by an exponential function called “warp factor”. This modelpredicts KK graviton resonances with both weak scale masses and couplings to matter. In its simplestform, with only one extra-dimension, two distinct branes (the TeV brane and the Planck brane), and withall of the SM fields living on the TeV brane, the Randall-Sundrum model has only two fundamentalparameters: the mass of the first KK state m1 and the parameter c = k/MPL, where k is related to thecurvature of the 5-dimensional space and MPL is the effective Planck scale. The parameter c governsthe width of the resonances, and is expected to be not far from unity.

Direct production of Randall-Sundrum resonances (pp" G) can lead to spectacular signals, forinstance in the clean di-lepton decay mode (G" ""). They should be observable already in the first yearsof LHC running if m1 is in the range 1-3 TeV. In addition, their properties (e.g. their spin-2 nature)can be measured and should distinguish them from e.g. Z " production [39]. Figure 19 summarises95% C.L. exclusion limits in the plane m1 versus c-parameter. It shows the present constraints from

29

hep-ph/0204087


What if there is no natural solution to the hierarchy problem?

• Split Susy is a scenario which is not motivated by solving the hierachy problem

• It ignores the fine-tuning of the Higgs mass

• From string theory landscape suggests it might be a statistically reasonable coincidence (like the apparent sizes of the sun and moon)

• In the end the models look very much like supersymmetry (with most of its desirable consequences) but with one big difference

• Large mass splitting between new scalars & fermions

• Long-lived gluinos

N. Arkani-Hamed, SavasFest 2012


Impact of MH on Split SUSY = “Mini Split”

• If the Higgs is ~125 GeV, the SUSY breaking scale in split SUSY can’t be that high (i.e. the “split” is smaller)

• Long-lived particles, not that long-lived

• cτ of ~100 µm to ~1 cm

• An experimentally accessible (but currently mostly overlooked range)

• If Nature is not natural, we may need a detector optimized for SUSY with this type of displaced decays


Should be skeptical of theoretical predictions

• Until we know what the new physics will be, we should be skeptical

• Two things we can do in any event

• State generic physics goals that are broadly well motivated

• Ask what is limiting physics in the current detector, or will be limiting it at higher luminosities

SUSY Spectrum, 1984

Text

Over 3 decades of susy: seismic shifts!L. Hall, SavasFest 2012


Generic Physics case for HL-LHC/HE-LHC

• Can say some general things (mostly taken from talk by M. Mangano in 2008). Will need HL-LHC to:

• Improve measurements of new phenomena seen at the LHC. e.g.

• Higgs couplings and self-couplings• Properties of SUSY particles (mass, decay, BR,

etc)• Couplings of new Z’ or W’ gauge bosons (e.g. L-R

symmetry restoration)• Detect/search low-rate phenomena inaccessible at

the LHC. e.g.• H→μ+μ–, H→Zγ• top quark FCNCs• WW scattering (especially if no higgs observed)

• Push sensitivity to new high-mass scales. E.g.• New forces ( Z’,WR ) • Quark substructure• Though these more of an argument for HE-LHC

10-1

1

10

10 2

10 3

3 3.5 4 4.5 5 5.5 6 6.5 7Mass of Z/, TeV

Num

ber o

f eve

nts

Fig. 17: Expected number of Z!!µ+µ", e+e" events in both experiments for integrated luminosities of 300 fb"1 per experi-ment and 3000 fb"1 per experiment.

4.7 Extra-dimensionsTheories with large extra-dimensions, which aim at solving the hierarchy problem by allowing the gravityscale to be close to the electroweak scale, have recently raised a lot of interest. They predict new phe-nomena in the TeV energy range, which can therefore be tested at present and future colliders. Severalmodels and signatures have been considered in the study presented here. They are discussed below.

4.7.1 Direct graviton production in ADD modelsIn these models [37], the extra-dimensions are compactified to the sub-millimiter size and only gravityis allowed to propagate in them, whereas the SM fields are confined to a 4-dimensional world. Gravitonsin the extra-dimensions occupy energy/mass levels which are separated by very small splittings, andtherefore give rise to a continuous tower of massive particles (‘Kaluza-Klein (KK) excitations’). Thepresence of additional dimensions can therefore produce new phenomena involving gravitons, such asdirect graviton production at high energy colliders.The most sensitive channel at the LHC should be the associated production of KK gravitons with a quarkor a gluon. The resulting signature is an energetic jet plus missing transverse energy, since the gravitonsescape detection. The cross-section depends on two parameters, the gravity scale MD and the numberof extra-dimensions !, and decreases with increasing values of both MD and !. The background isdominated by the final state Z(!"") + jets.

The discovery potentials of the LHC and SLHC are compared in Fig. 18. It can be seen thata factor of ten in luminosity would improve the LHC mass reach by typically 30%. Major detectorupgrades are not crucial for this physics, since the search is based on events with jets and missing energyin the TeV range. For comparison, doubling the LHC energy but keeping the instantaneous luminosityof 1034 cm!2s!1 would approximately double the reach inMD for any value of ! [4].

28

hep-ph/0204087


Actual CMS detector limitations in current physics program should also drive upgrade

• Looking at current physics performance, asking the PAGs/POGs, what are potential limitations of CMS?

• Too much material, especially in forward region (effects ECAL and tracker performance)

• Perhaps we have too much redundancy in tracking?

• Large extrapolation between last pixel layer and first TIB layer means track seeds can only come from pixels

• Addressed in upgrade pixel detector, but should bear in mind for Phase 2 tracker

• At present, high pT btagging is problematic. Breaks down completely above 1.5 TeV

• If SUSY is high pT and displaced (a la mini split) this would be an issue.

• L1 trigger thresholds on single leptons are high and rising

• Issue for SUSY with compressed spectra AND Higgs physics


Importance of physics input to future upgrades

• These responses (some of which are contradictory) raise important questions about any upgraded CMS detector that can only be guided by physics input, based on latest knowledge of what physics we need to do and how actually perform the analyses. Upgrade PFlow

– Hadronic showers develop longitudinally with finite uncertainties in the cluster centroid locations in eta/phi

– Granularity should be thought of as “Granularity significance” of separating two clusters in eta/phi

Upgrade algorithm allows a wider window to associate HCAL clusters With a charged track and thereby reduces the rate of false neutral hadron Identification – neutral hadrons are the primary limitation in the PFlow MET

Depth 3

Depth 2

Depth 1

Tracker

ECAL

C. Tully’s talk CMS upgrade week

• All analyses now critically dependent on PF

• Need to make sure upgraded detector is designed with PF in mind

• Likewise need to do PF studies of upgraded geometries to inform this process

• Dedicated effort that looks at CMS holistically needed (GED for upgrade)


Another example where physics input is needed, proposed Track Trigger

• Proposed design is for a triggering tracker, not necessarily an optimal tracker

• Assumption is that need a track trigger to cope with L1 muon rates (w/2012 data this seems to be justified)

• But also assumes that need to trigger on muons out to eta of 2.5• This comes from TDR requirement

that need to trigger on > 50% W’s• A good rule of thumb for the

physics program of the last 20 years, it may/may not be the best benchmark for the next 20 years

• Whether this is or not is a (new) physics question

General concept !  Silicon modules provide at the same time “Level-1 data” (@ 40 MHZ),

and “readout data” (@ 100 kHz, upon Level-1 trigger) "  The whole tracker sends out data at each BX: “push path”

!  Level-1 data require local rejection of low-pT tracks "  To reduce the data volume, and simplify track finding @ Level-1

#  Threshold of ~ 1÷2 GeV ⇒ data reduction of one order of magnitude or more

!  Design modules with pT discrimination (“pT modules”) "  Correlate signals in two closely-spaced sensors

#  Exploit the strong magnetic field of CMS

!  Level-1 “stubs” are processed in the back-end "  Form Level-1 tracks, pT above 2÷2.5 GeV

#  To be used to improve different trigger channels

April 13, 2012 D. Abbaneo - CMS Upgrade Performance Workshop 5

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+$**$

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y z

“stub” L1 tracks

from stubs

“Long Barrel” Design

Anders Ryd Cornell University - USCMS Collaboration meeting, May 16-19, 2012 Page:18

716

Digis

4.5 2

-210 0 210 -270 0 270cm

Layer 4

Layer 1

Hit Rates

Clusters

16 MHz/cm2 corresponds to 0.8 hits/cm2 per

crossing for 20 MHz bunch crossing rate

Scale difference between full and fast

simulations due mostly to delta rays not

included in the fast simulation

Shape difference at high η values are due to

limitations of the fast simulation

Differences between full and fast simulations

significantly reduced with clusters

Stub rate significantly reduced in the high eta

region

interaction region requirement to form a stub

Documented in detail in DN-2012/003

Could less material in forward region be more important than triggering there?


Part 2: physics after LS1

CMSUpgradeOrganizaRon

ConsolidaRonandUpgradesLS1…TDRProjectsPhase2

Upgrade Project Office

Project managers: Didier Contardo, Jeff Spalding

Pixel Detector R. Horisberger

Cross-organization Representatives

Trigger Performance and Strategy Working Group

Phase II Forward Detector Working Group

Silicon Tracker D. Abbaneo

ECAL E. Auffray, S. Singovski

HCAL D. Baden, C. Tully

CSC D. Loveless

DT C. Fernandez Bedoya

RPC G. Iaselli

L1 Trigger A. Tapper

DAQ A. Racz

BRM A. Dabrowski, D. Stickland

Infrastructure and Common Projects: W. Zeuner

Track Trigger Task Force M. Mannelli

Forward Calorimetry Task Force B. Cox, R Ruchti

Physics Coordination

DPC: Chris Hill

Tech. Coordination

DTC: Wolfram Zeuner

TwoWGsbeingformedtodeveloplong‐range

strategiesfortheCMSUpgradeProgram

2UWk21/5/12

Allconveners

aremembers

ofanUpgrade

ProjectOffice

meeRngby‐

weekly


Physics studies in PAGs since January

• Since January, physics coordination has been asked to take on upgrade studies• Bring physics expertise• Provide resources

• This activity has begun in earnest in April (after Moriond)• HIG and SUS are pursuing several upgrade analyses (status reports in TDR

sessions this week) • These studies are being supported by PPD, Offline, Computing• So far, due to the urgency of the timescale, these efforts have been limited to

studies for the LS1 TDRs• Need to expand these activities to physics studies for HL-LHC (and HE-LHC)

• EXO getting involved now (e.g. heavy gauge bosons - W’,Z’)• If existing efforts being done in upgrade community, need to be brought into

PAGs• Should expand activity to POGs, coordinated by GED effort


General Strategy for Physics Case for TDRs

• Early on agreed upon general statements about what physics can demonstrate upgrade

• Pixels - analyses with b’s, photons (e.g. Higgs, SUSY)• Trigger - analyses with tau’s (e.g. Higgs)

• HCAL - analyses with jets, MET (e.g. VBF, SUSY)• Based on this, HIG & SUS were targeted as critical PAGs that must undertake upgrade

studies • Overall theme more compelling than disjointed studies (possibility of a physics TDR)

• E.g. If Higgs signal observed in 2012, clear physics goal is measuring Higgs couplings to establish conclusively if a SM Higgs (or not)

• Fermionic modes are thus critical, i.e. bb, tau tau• For specific analyses to pursue, needed to iterate with conveners to select appropriate

physics studies that make the physics case, but can also be delivered on time (and with minimal disruption to PAG data analysis)

• Manpower & expertise availability


Overview of HIG Studies (M. Klute)

• New Higgs SubGroup formed - “Future Higgs Analyses” (M. Klute & P. Giacomelli)

Markus Klute - MIT

“Future Higgs Analyses” group• started operating Mar 21st with first meeting

• mandate to study future, beyond 2012 data taking, Higgs physics program

• Higgs properties (mass, spin, width, couplings)

• add (explore) rare decays and difficult channels (self coupling)

• untapped non-SM modes

• VV scattering

• support CMS upgrade program

• begin with detector-driven approach

• later reverse strategy in order to guide upgrades based on physics needs

• studies for European Strategy group

• group is setup horizontally in the landscape of Higgs sub-groups

2Markus Klute - MIT






• VV scattering






2

Markus Klute - MIT






• VV scattering






2

Markus Klute - MIT

Samples• general

• use PYTHIA for background and PYTHIA/POWHEG for signal as done for 8 TeV production

• generate at 14 TeV

• generate with default and upgrade geometry

• have to find agreement on PU scenario (<PU> = 50, 25ns)

• standard candles (1M events each)

• Z boson production to e, μ and τ• top-pair production

• signal processes (200k events each)

• H ➛ bb: VH, ttH

• H ➛ ττ: ggH, VBH, VH

• H ➛ γγ: ggH, VBF, VH

• H ➛ ZZ(4l): ggH, VBF

• Higgs gen contacts (Christophe and Nicolas) will provide snippets and LHE files

4

• Samples requested at 14 TeV, <PU> = 50:

Markus Klute - MIT

Samples• general

• use PYTHIA for background and PYTHIA/POWHEG for signal as done for 8 TeV production

• generate at 14 TeV

• generate with default and upgrade geometry

• have to find agreement on PU scenario (<PU> = 50, 25ns)

• standard candles (1M events each)

• Z boson production to e, μ and τ• top-pair production

• signal processes (200k events each)

• H ➛ bb: VH, ttH

• H ➛ ττ: ggH, VBH, VH

• H ➛ γγ: ggH, VBF, VH

• H ➛ ZZ(4l): ggH, VBF

• Higgs gen contacts (Christophe and Nicolas) will provide snippets and LHE files

4


Overview of HIG Studies (M. Klute)

• Ongoing Studies:

Markus Klute - MIT






• VV scattering






2Markus Klute - MIT






• VV scattering






2

Markus Klute - MIT

Studies • perform POG-like studies in the context of Higgs searches

• Jets/MET

• forward jet tagging

• b tagging

• lepton (e,μ,τ) identification

• photon identification

• evaluate impact on Higgs measurements by comparing with current analysis (default geometry)

• VBF channels: jet tagging, (di-jet mass resolution)

• Higgs strahlung (ZH): lepton id

• H ➛ bb: b-tagging, (di-jet mass resolution)

• H ➛ ττ: MET resolution, jet tagging, tau id

• H ➛ γγ: photon id

5

Talks on status of studies by M. Grimes last week, CMS Upgrade Week 23Monday, May 28, 12

Overview of SUS Studies (D. Stuart)

SUSY Meetings •  We will be using our meeting time and/or hold special

meetings for this work to be discussed –  e.g. special meeting last Friday

•  Some work already ongoing but some areas not covered

8

Overview of Upgrade SUSY Analyses

•  We have identified the following SUSY analyses to motivate the upgrades:

– γγ+MET – All-hadronic + b’s search with MT2 – Searches with taus – Stop analysis in single lepton channel

2

Important but potentially difficult SUSY searches

Analyses which will benefit from more than one (or all) upgrades

Talks on status of studies by R. Stringer & T. Kamon last week, CMS Upgrade Week


Overview of SUS Studies (D. Stuart) Upgrade SUSY Analyses (Pixels)

– Pixels 1.  γγ+MET (R. Stringer)

– Upgraded Pixel has: »  Less material (less conversions) »  Fourth layer (another chance for hit in pixel)

–  Should improve efficiency and fake rate.

2.  MT2 + b (ETH) –  e.g. could study channels such as T1bbbb –  sensitive to changes in efficiency and fake rate for additional tags beyond the two real b's

4


Overview of SUS Studies (D. Stuart) Upgrade SUSY Analyses (L1)

– L1 trigger •  SUSY benchmarks for studying

improvements in tau trigger (T. Kamon) –  e.g. important for searches with taus

especially in all hadronic environment – Will rely on flexible requirements of a global

trigger

•  Issues for compressed SUSY and stop production (P. Bargassa)

–  e.g. important to be able to select low pT leptons and soft jets

•  In general, need volunteers to help out (some candidates with interest).

7


Overview of SUS Studies (D. Stuart) Upgrade SUSY Analyses (HCAL)

– HCAL 1.  γγ+MET (C. Tully, et al)

–  Improvement to photon ID » Current focus is on photon object ID and triggers »  Separation of layer-0 directly removes the bulk of pileup

contributions and their fluctuations from HCAL isolation & H/E »  Techniques like rho-subtraction suffer from E/H fluctuations » HCAL energies have higher S/N – more sensitivity »  Timing information suppresses out-of-time pileup

– MET improvements have not been studied

5 27Monday, May 28, 12

Overview of SUS Studies (D. Stuart) Upgrade SUSY Analyses (HCAL) –  HCAL

2.  stop analysis using single lepton channel (Rochester, DESY) For example: –  T1tttt

»  gives 4 b's »  likely most sensitivity from the >=3 tag sample »  Again, sensitive to changes in efficiency and fake rate for

additional tags beyond the two real b's from the dominant top background

–  T2tt »  2 b's just like top »  being able to fully reconstruct the event will be important for

understanding the background and that will benefit from maintaining efficiency

»  Lower pT leptons and lower MET challenge »  Can also use this analysis to also study the Pixels and/or L1. Need

(wo-)manpower

6


Looking Further Ahead

• The post LS1 (~300 fb-1 at 14 TeV) physics case is (while still very dependent on this year’s results) relatively easy to define

• The case for HL-LHC (~3000 fb-1) is less easy to state now• Nevertheless, must define/update physics goals, supported by (new) studies• Guide detector design; long lead-time for upgrades• ESPG, Snowmass, TDRs, etc.

• As we have been doing for post LS1 studies, need to expand upgrade activities within physics (with offline & computing support) to studies for HL-LHC (and HE-LHC)• Existing efforts being done in upgrade community need to be brought into

PAGs• PAGs other than HIG, SUS need to get involved (EXO is starting)• Start POG activities on improvement needed for reconstruction

• GED workshop on June 15th


How to organize LS2, LS3+ studies?

• It seems that dedicated PAG sub-group (a la HIG) is way to go

• Some efforts already exist at varying levels for various sub-detector upgrades

• As a first step I have emailed each of the PM’s to have them bring any ongoing studies to my attention

• From the responses I have received, it seems there is not so much activity, and what is there is limited to performance studies

• Clear that physics has a role to play to bring these activities (or launch them where they are absent) under one umbrella

• Establish (important) physics benchmark measurements/searches for proposals to be evaluated against

• Allow a unified look at performance of the entire upgraded detector rather than sub-systems in isolation - crucial to get best performance for CMS as well as to avoid over-design


European Strategy Group Report, Snowmass 2013, etc.

• Long term studies are not just for upgrade design and TDRs, also inform national/international strategic planning

• HIG, SUS, EXO are preparing studies for European Strategy Group Report due this summer

• Next year in the US, there will be Snowmass 2013 which we should likewise prepare studies for

• Since more time, analyses can be more elaborate

• Perhaps we will produce a new PDTR next year

?


Summary & Next Steps

• Right now two big questions in LHC physics is EWSB and Naturalness

• These questions have guided design & construction of CMS

• But very soon we will know the answer to the first and not that long after the second

• Answers to this will determine HL-LHC program and should guide design of upgrades

• Detector requirements may be different depending on the physics

• Structure now in place, and activities launched, to carryout physics studies to support upgrade TDRs

• But TDRs are not the end of this story, beginning to think about structure that will endure through LS1 and into 13/14 TeV operation (and planning beyond towards HL-LHC)

• Clear that coordination of activities, with input from physics, is needed

• Opportunity for involvement in studies to shape design of future CMS detector


cms physics beyond ls1chlebana/cms/hcalupgrade/... · i’ll use two meanings of the word physics...

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